The Stockholm Convention aims to protect human health and the environment from Persistent Organic Pollutants (POPs). These synthetically made compounds are extremely harmful materials which since many decades have spread in the environment, poisoning the atmosphere, the surface water, the soil and the groundwater. Currently there are twelve chlorine containing POPs on the list of the Convention. Most of them are pesticides (Aldrin, Chlordene, Dieldrin, Endrin, Heptachlor, Hexachlorobenzene, Mirex, Toxaphene), agents against malaria vectors (DDT), compounds used in industry (polychlorinated biphenyls) and materials released during industrial activities (Polychlorinated dibenzo-p-dioxins and dibenzofurans, Hexachlorobenzene).
As a result of the inventory of the stocks, the export and import of such pollutants, the most serious problem turned out to be the annihilation of polychlorinated biphenyls (PCBs) oils containing PCBs like used transformer and hydraulic oils, lubricants, etc.
The polyhalogenated hydrocarbons, especially the aromatics, produced during decades are chemically very stable and persistent materials. There are 209 PCB congeners.
The utilization field of polychlorinated aromatics became much wider (cement and paint softeners, stabilizer additives for PVC, used as insulators in electric wires, fire retardants, cutting oils, lubricating oils, hydraulic oils, floor polishing materials, sealing compounds, vacuum oils, etc.). Their production peaked in the sixties. A large amount thereof entered the environment and thereby polluted soil, groundwater, rivers, lakes, oceans and air. As their natural biological decomposition is very slow, the elimination of the used polychlorinated aromatic hydrocarbons stored as wastes is a worldwide problem.